Prior to the development of the present invention, as is generally quite well known in the railroad industry, such slackless type drawbar assemblies have been in widespread use for several years to couple together adjacently disposed ends of a pair of railway freight cars in a substantially semi-permanent fashion.
Freight cars coupled together in this particular manner are usually of the type used in the railroad industry in what is most commonly referred to as dedicated service. Such dedicated service type railway cars include; by way of example only, freight cars which are used to haul coal, coke, and/or various other types of raw minerals, light truck and automobile transport carriers, tank cars used for transporting various types of liquids, as well as, freight cars which are often used to transport various types of building materials. A few examples of raw minerals transported in these dedicated service type railway cars include; various ores, cement and stone. The various types of liquids which are known to be transported by such dedicated service type railway cars will at least include a number of different chemicals.
One prior art slackless type drawbar assembly, presently known to applicants, is taught in U.S. Pat. No. 5,000,330. Illustrated therein is a pair of freight cars which have their adjacently disposed ends connected together by the slackless drawbar assembly. This, particular, slackless type drawbar assembly, as illustrated in FIGS. 2 and 3, is constructed in such a manner that will enable it to operate with a positioning apparatus.
This drawbar is manufactured from a metal casting, such as steel, and includes a shank portion. Such shank end portion is provided with a non-rotatable fixed end portion that is movably secured within one end of the center sill portion of the car body member. The shank portion includes a rotatable end portion that is secured within one end of the center sill portion of an adjacently disposed car body member. Each of the fixed end portion and the rotatable end portion of such slackless drawbar assembly extends into pocket castings and follower blocks which differ slightly but otherwise the center sill portions and pocket casting parts of both car body members are substantially identical and are best seen in the enlarged view of FIG. 3A.
The fixed (i.e., non-rotatable) end portion is held in place in the center sill portion of such car body member by a key and against a follower member disposed in a pocket casting. The pocket casting is received within the center sill opening, which is defined at it's inboard end by rear stop members. These rear stop members abut against side wall extensions provided on the pocket casting. A shim member may be disposed intermediate the rear stop members and the side wall extensions of such pocket casting. The shim member may be replaced with a thicker shim member, should excessive wear require the pocket casting to be spaced a further distance from the rear stop members.
The pocket casting includes a cup-like cavity which is formed by an end wall portion and an encircling skirt portion of such pocket casting. Within such cup-like cavity, the end wall portion presents an inclined face which is formed with a generally shallow V-shaped concavity (as best seen in FIG. 2).
As can best be seen in FIG. 3A, there is a wedge shaped member seated in the cup-like cavity. This wedge shaped member is positioned to frictionally bear against the face of the pocket casting. Such wedge shaped member includes an inboard inclined bearing, or friction, surface which is convex-shaped so as to be complementary to the face of the pocket casting. An outboard wedging surface disposed on the wedge shaped member is formed as a shallow V-shaped concavity that bears against a follower block. The follower block member is formed with a complementary inboard wedging convex V-shaped face which is positioned to bear against such concave outboard surface of the wedge shaped member.
One embodiment of the wedge shaped member, as is best seen in FIGS. 9 and 10, is provided with two laterally projecting guide tabs in order to minimize the lateral shifting thereof. Lifting or positioning lugs, of generally hook shape, also project from the sides of such wedge shaped member. Access to both the lugs and the wedge shaped member is made possible by the provision of an access opening or slot formed in the skirt portion of the pocket casting and a corresponding aperture provided in the top web of the center sill portion and in a lower channel member (which supports such pocket casting) thereby enabling the insertion of a tool to engage the lugs of the wedge shaped member without having to remove the pocket casting itself. The wedge shaped member may, also, be vertically positioned by inserting a tool through an opening, or slot, formed in the pocket casting and the side walls (not shown) of the center sill portion.
Another embodiment of such wedge shaped member, as shown in FIG. 3A, is provided with a depending tail piece portion. This tail piece portion of such wedge shaped member extends in a downwardly direction through bottom openings formed in the pocket casting skirt portion and in a lower channel. In this manner, the vertical repositioning of such wedge member is facilitated.
The outboard face of the follower block member is formed with a spherical concave face which matingly engages a convex spherical butt on the fixed end portion of the drawbar shank. Retaining the fixed end portion within the center sill pocket is a key member which extends through slots provided in such center sill side castings and a key slot formed through the drawbar shank.
The key slot end portion is formed with a concave surface which is concentric to the follower block spherical concave face and the convex spherical butt end of the drawbar shank. Seated and bearing against the concave surface is a complementary convex face of a key bearing block. This arrangement facilitates horizontal angling of the drawbar assembly while the fixed end is held by the key. A groove of semicircular cross section along it's edge opposite such convex face is formed in the bearing block. Seated within the groove is a complementary convex edge of the key. A resilient pad is disposed intermediate the top of the key slot and the top face of the key to permit vertical angling of the drawbar assembly while maintaining the key seated in the groove of the bearing block. This facilitates the vertical angling of the drawbar assembly on the key.
The rotatable end of the drawbar assembly is, also, received in a center sill opening of the car body. Within the center sill opening is a pocket casting, having a wedge, and a follower block of structure similar to that described in connection with the stationary or fixed end, although it may extend outwardly of the pocket casting to engage a larger portion of the rotatable end. A shim may be disposed between the rear stop members and the pocket casting wall as, also, described at the fixed end. Similar wedge access slots and apertures are, also, provided in the pocket casting and the top web and sides of the center sill portion.
The rotatable end of the drawbar assembly is formed as a ball having two spherical portions generated from a common center disposed inwardly and outwardly, respectively, of the follower block. These spherical portions are attached to a cylindrical barrel of smaller diameter (to fit within the center sill pocket). The outward spherical surface engages the spherical concave face of the follower block. Retaining the ball end within the center sill pocket is a bottom pulling block segment and an interlocking top pulling block segment (shown in detail in FIGS. 4-8) which engage the inward spherical surface.
The bottom pulling block (as shown in FIGS. 6-8) is generally in the form of a semicircular ring provided with a base portion and a pair of generally upstanding walls portion. The block segment is formed with a concave partially spherical surface which engages the inwardly disposed portion of the spherical ball. The base of the lower pulling block is provided with a generally "V" shaped notch which reduces the lowermost bearing area of the concave surface. All of the spherical surfaces are concentric to lessen the resistance to angling of the drawbar assembly during curve negotiation and the rotary dump operation.
A pair of lug members project from the top of the block and are seated in notches or recesses formed in the upper pulling block segment. Such upper pulling block segment (as shown in FIGS. 4 and 5) is, also, in the general form of a semicircular ring and in which the inner surface is formed as a partially spherical concave surface. This concave surface bears against the inwardly disposed portion of the spherical ball and coacts with the bottom pulling block concave surface to embrace the ball. The upper and lower pulling blocks are formed with complementary semicircular openings through which the shank of the drawbar assembly extends. It is to be noted that the partially spherical surfaces are non-symmetrical with the concave surface of the lower pulling block being notably larger.
Restraining the pulling blocks against longitudinal movement out of the center sill opening is a front stop member. A removable cross plate member is fastened by bolts or the like, across the bottom flanges of the center sill to support the pulling blocks within the opening of such center sill. Channels are, also, removably secured, by bolts or the like, across the center sill to support the pocket casting and the wedge for both the fixed end of the drawbar assembly as well as the rotatable end. This reference considers two features of the construction receiving the drawbar assembly rotatable end to be important. These features are a horizontal shim positioned between the upper pulling block and the top of the center sill, and a cradle positioned on a cross plate to support the drawbar end ball. Both features are illustrated in FIG. 3A and provide means to maintain the pulling blocks, ball and follower in proper orientation.
It is taught that the centers for generating the arcuate surfaces should be horizontally aligned; however when draft (pulling) loads are applied to the drawbar assembly, the ball will tend to rise across the lower pulling block and spread the pulling blocks apart. Should that occur the aforementioned centers for the pulling blocks will separate vertically and lose concentricity with the abutting ball surface portion. The result is to increase resistance to angling and rotation of the drawbar assembly. Additionally, the ball moves so as to cause the wedge member to drop and reposition the follower thereby reducing the available wedge and follower adjustment for wear compensation.
The cradle serves to support the drawbar assembly ball at the proper level for alignment to maintain concentricity with both the follower and pulling block during or immediately after the system is unloaded such as the brief transition from buff to draft loading (or vice versa) or when the car is rotated and the wedge member slightly retracts or during partial disassembly. The cradle has an arcuate surface that is concave to receive the barrel portion of the ball.
Should a slack adjusting wedge member, and/or adjacent parts, become worn to the point such that the wedge member will no longer function to eliminate slack, the wedge member can be lifted by extending a tool through the openings and apertures into engagement with the wedge lugs.
Another method is to insert a tool through the bottom openings in the pocket casting skirt portion and lower channel and applying a vertical force to the bottom of wedge shim, or by pushing upward on a wedge tail piece if so provided. This will allow the worn parts to be spaced further from the rear stop members and a shim member to be disposed between the rear stop members and a the pocket casting wall, or a shim to be replaced with a thicker shim to compensate for dimensional changes in worn but still usable parts. Similarly if it becomes necessary to disconnect the drawbar assembly, this can be is accomplished at either or both ends by lifting the wedge member and removing either, or both, the key and the pulling blocks (by first removing the cross plate).